factory modified so that config is injected into RoleMapper
constructor added to initialise config so that insert() method would have access to the name of the linker table
user_role_id key added to config
role_id of user entity modified to be the id of the role table record for the user role. Originally this was a string value of 'user'. Numerical id of user role obtained from new key in the linker.config.php file so this is user configurable to suit how user has set up the role table.
Added note to user that it is now necessary to add the user_role_id value to the linker.config.php file.
Tidied up markdown in readme.md
More markdown tidying.
Merge pull request #12 from mikekelly1/issue#9

Issue#9 thanks to mikekelly1